Abstract The goal of Core B is to provide the leadership, administrative oversight as well as statistical analysis and related quality control to insure the completion of the specific aims of Projects 1 through 4. This is a multifunctional Core that provides a broad array of administrative and biostatistical services, and overall leadership to support the smooth operation and optimal productivity of the Program Project. Dr. Stampfer, the Core Leader, has been an investigator with the Nurses' Health Study and with several of the other cohorts included in the proposed Program Project since 1979, and most of the investigators in this Core and the overall Program Project have been close colleagues and collaborators for many years, with high demonstrated productivity - testimony to the strong administration and leadership of this Core over the years. Dr. Stampfer is also Principal Investigator of the pending UM1 grant (CA186107, priority score=10) which will support the infrastructure of the overall Nurses' Health Study; this helps to guarantee that the administration and leadership within this proposed Program Project will be well-coordinated with the overall Nurses' Health Study. Specifically, key activities of this Core with respect to Leadership and Administration will include: regular meetings of Program Project investigators and staff to review progress, provide results, and exchange key practical and scientific information (all investigators and staff across all participating epidemiologic studies included in the Program Project attend this meeting); documentation of the Program Project meetings; participation in annual meetings of the cohort External Advisory Committee of national experts in relevant areas; monitoring of Program Project-related IRB activities; and completion of annual NIH progress reports. Key activities of the Core with respect to Statistical Analysis include: biostatistical and programming support for the projects; quality control of all programming to ensure publications are accurate and error free; data documentation; and interaction with Core A to ensure that data warehousing of biomarkers allows efficient statistical analysis of complex data. This Core will clearly provide critical services to all four Projects in this proposed Program Project.